Radiation recuperator



Oct. 10,1967 WSEEHAUSEN Y 3,346,042

RADIATION RECUPERATOR Filed Oct. 13,1965 I s Sheets-Sheet 2 INVENTORB. uaasr 14 55554055 I rm/ W5.

Oct. 10, 1967 J. w. SEEHAUSEN 3,346,042

RADIATION RECUPERATOR Filed Oct. 13, 1965 3 Sheets-Sheet 3 INVEN TOR. JOBST 144555/744055 United States Patent 3,346,042 RADIATION RECUPERATOR Jobst W. Seehausen, Upper St. Clair Township, Pa., as-

signor to General Ionics Corporation, Bridgeville, Pa., a corporation of Pennsylvania Filed Oct. 13, 1965, Ser. No. 495,424 14 Claims. (Cl. 165-154) This invention relates to radiation recuperators, and more particularly to vertical recuperators that receive hot flue gases at their lower ends.

Recuperators of this type include a vertical metal cylinder that is open at top and bottom so that hot flue gases can flow through it, a metal shell encircling the cylinder and spaced from it, and an insulating lining for the shell spaced from the cylinder to form a vertical air passage around the cylinder closed at top and bottom except for a cold air inlet at one end and a hot air outlet at the other, whereby the flue gases and air flow through the recuperator and the air is heated by the gases.

It is among the objects of this invention to provide a radiation recuperator which is more efiicient, which has more strength at high temperatures, which is less likely to overheat and which is easier to assemble than heretofore.

The invention is illustrated in the accompanying drawings, in which FIG. 1 is a vertical section through my radiation recuperator;

FIG. 2 is an enlarged fragmentary side view of the cylinder and section of the shell and lining;

FIG. 3 is a fragmentary horizontal section taken on the line III-III of FIG. 2; and

FIG. 4 is a vertical section through a modified embodiment of the invention. Referring to FIG. 1 of the drawings, the recuperator is shown mounted on a suitable foundation 1 provided with a large vertical passage 2 that receives hot flue gases from a furnace (not shown). The outside or shell of the recuperator is a metal cylinder 3, the lower portion of which may be flared downwardly to provide a large base to lend stability to the recuperator. The lower end of the shell is securely anchored to theifoundation concentric with the opening therethrough. Inside of the shell there is a metal cylinder 4 substantially coextensive in length with the shell. The cylinder is considerably smaller than'the shell to provide a wide annular space between them. The upper end of the cylinder is suspended from a metal ring 5 secured to the top of the shell, on which a stub stack 6 may be mounted. The ring closes the top of the space between the shell and lining. The lower end of the cylinder does not rest on anything and therefore is free to expand downwardly when heated. However, an encircling ring 7 is secured to the lower end of the cylinder, with the outer edge of the ring connected by an expansion joint 8 to the surrounding lining 9 of the shell.

This lining, the purpose of which is to insulate the shell from the heat radiated by cylinder 4, is spaced from the cylinder in order to form a vertical air passage 11 around it. The upper end of the shell is provided with a lateral inlet 12 for cold air, while the lower end of the shell is provided with a lateral outlet 13 for hot air, this inlet and outlet communicating with the opposite ends of the vertical air passage 11. In some cases, however, the air flow may be reversed, and the flue gases may even enter from the top and flow out of the bottom of the recuperator. The insulating lining need not extend entirely to the top of the shell, but can terminate below the air inlet. When that is done, a relatively short cylindrical partition v 14 is mounted in the shell flush with the inner surface of the lining and extends up to a point a short distance from Patented Get. 10, 1967 suspension ring 5 so that entering air will have to flow upwardly in the shell and across the top of the partition in order to enter the top of the air passage. The air flowing down through the lower portion of the air passage is confined by another cylindrical partition 15 suspended from the upper end of the tapered lower portion of the lining. The lower end of this partition is spaced from the bottom ring 7 of the cylinder to permit the air to leave the air passage and enter the air outlet 13.

At predetermined levels in the recuperator there are metal rings 17 secured tightly to the inside of the shell, which extend into the lining for three purposes. One purpose is to relieve the lining below each ring from some of the weight of the lining above it, a second purpose is to stiffen the shell and the other purpose is to interrupt and deflect back into air passage 11 any downwardly flowing air that may have penetrated between the lining and the shell. In other words, any such air, upon reaching one of the metal rings, will be stopped from flowing further down between the lining and shell and will be deflected inwardly by the ring back into the air pass-age.

To increase the heat transfer from the inner cylinder of the recuperator to the air flowing down through the air passage around the cylinder, the outside of the cylinder is provided with a large number of metal fins 19. These fins extend lengthwise of the cylinder in substantially parallel vertical rows. Each row of fins is composed of a plurality of relatively short fins that are spaced apart vertically. Also, the fins in each row are inclined in opposite directions alternately to form a zigzag line of fins. By breaking each row of fins up into a number of separate fins, no problems are caused by the diflerences in thermal expansion of the fins attached to the hotter and colder parts of the cylinder. Also, by inclining the fins in Opposite directions, they cause the air passing down through the air passage around the cylinder to become more turbulent and pick up more heat from the fins than otherwise would be the case.

In spite of the heat exchange between the hot gases and the surrounding air in the recuperator, the lower portion of the cylinder, being exposed to the hottest gases, becomes extremely hot, so it is desirable to strengthen it by metal reinforcing rings 21 that encircle it at vertically spaced intervals.

The faster the air flows down around the lower portion of the metal cylinder, the more rapidly it will remove heat from the cylinder and the cooler the cylinder will be maintained. Since the velocity of the air down through air passage 11 is a function of the width of that passage, it will be seen that a narrow passage would produce a high velocity of air. On the other hand, a narrow gap also increases the pressure drop of the air flowing through the passage and that should not be allowed to become excessive. Accordingly, only the lower portion of the passage is made narrow and that is done by moving the inner surface of the lining farther away from the encircling shell. This can be accomplished by making a thicker lining, but it is more desirable to use refractory blocks of uniform lateral thickness throughout the lining. When these blocks are moved inwardly to reduce the width of the air passage, they become spaced from the shell, as shown in FIG. 2. This space should be filled with other insulating material 23, asbestos paper being suitable for this purpose. For the same reason that the lower portion of the air passage is reduced in width, it also is desirable to reduce the width of the central portion, but not so much because the air velocity need not be so great in this cooler area as near the bottom. Therefore, the refractory blocks in this central area are spaced from the shell, but not as far as those below. The width of the different parts of the air passage preferably is such that the pressure drop of the air passing through it will be substantially the same as it would have been if the width of the passage from end to end were the same as the width of its central portion. This is accomplished by making the upper portion of the passage wider than would be the case if the passage had a normal uniform width from top to bottom. The Wide upper portion of the air passage also results in the upper portion of the cylinder being cooled less, so there is no danger of the moisture in the flue gas condensing on the inside of the cylinder. Of course, if the recuperator is one in which the air and gas flow are reversed, the upper end of the air passage is the one that should be more restricted.

In erecting this recuperator, the practice is to line the shell with refractory while it is lying horizontally and then insert the metal cylinder. Insertion of the metal cylinder while the shell is horizontal can be a diflicult operation, especially when it is surrounded by fins attached to its outer surface. To greatly facilitate insertion of the cylinder, a plurality of circumferentially spaced radial rollers are mounted in the shell along its length by supporting them in brackets 26 secured to the shell. The brackets extend through the refractory lining and support the rollers close to the cylinder, as shown in FIGS. 1, 2 and 3. The cylinder therefore can be rolled into the shell on the rollers. To prevent the fins from interfering with this operation, the vertical rows of fins must be spaced apart far enough to allow the rollers to pass between them. Also, there must be gaps in reinforcing rings 21 when the rollers are used. The rollers also serve the important function of centering the cylinder in the shell and maintaining it centered so that the air passage will have substantially the same width entirely around the cylinder and not be thicker at one side than at the other.

In the modification shown in FIG. 4 the recuperator is made in such a way that there is still more efficient heat exchange between the hot gases and the cold air because both countercurrent and concurrent flow of air is provided, and the construction is such that it is easier to inspect and clean the inside of the recuperator. Accordingly, this recuperator has two separate vertical sections, the upper one of which is entirely above the lower one and offset laterally relative to it. These adjacent ends are connected by a box-like structure. More specifically, the outer shell 30 and the refractory lining 31 of the lower section of the recuperator rest on a foundation 32 provided with a large vertical passage 33 for hot fiue gases. Spaced inwardly from the lining is a metal cylinder 34, the upper end of which is suspended from one end of the bottom of a refractory-lined box 35 supported by beams 36 or'the like. The box has a large opening 37 that connects the inside of the cylinder with the inside of the box. The annular space between the cylinder and the shell lining forms an air passage 38 which, in this case, has its inlet 39 near the bottom of the shell and its outlet 40 near the top. The entering cold air therefore first engages the hottest part ofthe cylinder and removes heat from it and flows upwardly parallel to the hot gas flow. The cylinder is provided with fins 41 like those shown in FIG. 1, and also with metal rings 42 projecting into the refractory lining from the shell. This section of the recuperator may also be provided with rollers 43 to facilitate insertion of the cylinder into the shell when they are in a horizontal position before erection.

The upper section of this recuperator likewise includes a metal shell 45 mounted on the end of box 35 opposite the lower section. The shell is lined with refractory 46 spaced from a finned metal cylinder 47 to provide a vertical air passage 48 between them. The upper end of the cylinder is suspended from a ring 49 attached to the top of the shell, while the lower end of the cylinder is slidably mounted in a large opening 50 in the top of the box. The upper end of the shell is provided with a cold air inlet 51, whil? its lower end is provided with a hot air outlet 52 so that there is counterflow of hot gases and cold air through this section of the recuperator. The two hot air outlets can lead to a common duct. Of course, the flow of hot gases is continuous from the lower end of the lower section of the recuperator up through the connecting box and out of the top of the upper end of the recuperator. Here again, the hot gas and air flows can be reversed if desired.

The reason that the two sections of this recuperator are offset laterally relative to each other is to permit the box 35 to be provided with openings in line with the two cylinders. Thus, the top of the box directly above the lower metal cylinder 34 is provided with a large opening 54 which normally is closed by a removable cover 55. Likewise, the other end of the box is provided in its bottom with a large opening 56 directly below the upper metal cylinder 47. This opening also is normally closed by a removable cover 57. By removing these covers, the condition of the inside of the cylinders can be observed and ready access can be gained to the inside of the metal cylinders for cleaning them whenever that become necessary. It also is desirable to provide the covers with sight glasses 58 and 59 so that the inside of the recuperator can be observed while it is operating, which is something which has not been possible heretofore.

According to the provision of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. A radiation recuperator comprising a vertical metal cylinder open at top and bottom for flow of hot flue gases therethrough, a metal shell encircling the cylinder and spaced therefrom, means connecting the upper end portions of the cylinder and shell to suspend the cylinder in the shell, means closing the space between the lower ends of the cylinder and the shell, an insulating lining for the shell spaced from said cylinder to form a vertical air passage around the cylinder, the shell being provided at its one end with a lateral air inlet into said passage and provided at its other end with a lateral air outlet from the passage, and vertically spaced metal rings secured to the inside of the shell and extending radially into said lining for supporting it and interrupting any flow of air vertically between the lining and shell.

2. A radiation recuperator as defined in claim 1, including a plurality of vertically and circumferentially spaced radial rollers in said air passage around the cylinder, and means secured to said shell at vertically spaced points therein pivotally supporting the rollers close to the cylinder.

3. A radiation recuperator as defined in claim 1, including a plurality of circumferentially spaced parallel rows of metal fins secured to the outside of said cylinder and extending lengthwise thereof, the fins in each row being spaced apart and disposed in a zigzag line.

4. A radiation recuperator as defined in claim 1, including a plurality of circumferentally spaced parallel rows of metal fins secured to the outside of said cylinder and extending lengthwise thereof, the fins in each row being spaced apart and disposed in a zigzag line, a plurality of vertically and circumferentially spaced radial rollers in said air passage around the cylinder, and means secured to said shell at vertically spaced points therein pivotally supporting the rollers close to the cylinder between some of said rows of fins, said rows being spaced far enough apart to permit the cylinder to be rolled into and out of the shell on the rollers during assembly or disassembly of the recuperator.

5. A radiation recuperator as defined in claim 1, including reinforcing rings encircling the hottest portion of said cylinder in engagement therewith.

6. A radiation recuperator as defined in claim 1, in which the width of said air passage around the hottest portion of said cylinder is less than the width of said passage around the coolest portion of the cylinder.

7. A radiation recuperator as defined in claim 1, in which the width of the central portion of said air passage is less than the width of its portion at the cooler end of the cylinder and greater than the width of the opposite end portion of the passage, the pressure drop of said passage being substantially the same as it would be if the width of the passage from end to end were the same as the width of said central portion of the passage.

8. A radiation recuperator as defined in claim 7, in which said lining is formed from refractory blocks of substantially uniform lateral thickness, the blocks at said central and opposite end portions of the passage being spaced from the shell, and insulating material fills the space between the shell and the blocks.

9. A radiation recuperator comprising a pair of laterally and vertically ofiset vertical sections with the upper end of one section adjacent the lower end of the other section, each of said sections being formed from a vertical metal cylinder for flue gases open at top and bottom and a metal shell encircling the cylinder and spaced therefrom, means connecting the upper end portions of each cylinder and shell to suspend the cylinder in the shell, means closing the space between the lower ends of the cylinder and the shell of each section, an insulating lining for each shell spaced from the encircled cylinder to form a vertical air passage around the cylinder, a box extending across the adjacent ends of said sections and having a bottom opening that opens into the top of the lower cylinder and having a top opening that opens into the bottom of the upper cylinder, the bottom and top of the box having a second pair of openings in line with said top and bottom openings respectively, removable means for closing said second pair of openings, one end of the lower shell being provided with a lateral air inlet into the adjacent air passage, one end of the upper shell being provided with a lateral air inlet into the upper air passage, the remaining ends of both shells being provided with lateral air outlets from the adjacent air passages, and vertically spaced metal rings secured to the inside of each shell and extending radially into the adjoining lining for supporting it and interrupting any flow of air vertically between the lining and shell.

10. A radiation recuperator as defined in claim 9, in which said air outlets are located adjacent said box.

11. In a radiation recuperator comprising a vertical metal cylinder open at top and bottom for flow of hot flue gases therethrough, a metal shell encircling the cylinder and spaced therefrom, means connecting the upper end portions of the cylinder and shell to suspend the cylinder in the shell, means closing the space between the lower ends of the cylinder and the shell, and an insulating lining for the shell spaced from said cylinder to form a vertical air passage around the cylinder, the shell being provided at one end with a lateral air inlet into said passage and provided at its other end with a lateral air outlet from the passage; the improvement comprising a plurality of vertically and circumferentially spaced radial rollers in said air passage around the chamber, and means secured to said shell at vertically spaced points therein pivotally supporting the rollers close to the cylinder.

12. In a radiation recuperator comprising a vertical metal cylinder open at top and bottom for flow of hot flue gases therethrough, a metal shell encircling the cylinder and spaced therefrom, means connecting the upper end portions of the cylinder and shell to suspend the cylinder in the shell, means closing the space between the lower ends of the cylinder and the shell, and an insulating lining for the shell spaced from said cylinder to form a vertical air passage around the cylinder, the shell being provided at one end with a lateral air inlet into said passage and provided at its other end with a lateral air outlet from the passage; the improvement comprising a plurality of circumferentially spaced parallel rows of metal fins secured to the outside of said cylinder and extending lengthwise thereof, the fins in each row being spaced apart and disposed in a zigzag line.

13. In a radiation recuperator comprising a vertical metal cylinder open at top and bottom for flow of hot flue gases therethrough, a metal shell encircling the cylinder and spaced therefrom, means connecting the upper end portions of the cylinder and shell to suspend the cylinder in the shell, means closing the space between the lower ends of the cylinder and the shell, and an insulating lining for the shell spaced from said cylinder to form a vertical air passage around the cylinder, the shell being provided at one end with a lateral air inlet into said passage and provided at its other end with a lateral air outlet from the passage; the width of the central portion of said air passage being less than the width of its portion at the cooler end of the cylinder and greater than the width of the opposite end portion of the passage, and the pressure drop of said passage being substantially the same as it would be if the width of the passage from end to end were the same as the width of said central portion of the passage.

14. A radiation recuperator comprising a pair of laterally and vertically offset vertical sections with the upper end of one section adjacent the lower end of the other section, each of said sections being formed from a vertical metal cylinder open for flue gases at top and bottom and a metal shell encircling the cylinder and spaced therefrom, means connecting the upper end portions of each cylinder and shell to suspend the cylinder in the shell, means closing the space between the lower ends of the cylinder and the shell of each section, an insulating lining for each shell spaced from the encircled cylinder to form a vertical air passage around the cylinder, a box extending across the adjacent ends of said sections and having a bottom opening that opens into the top of the lower cylinder and having a top opening that opens into the bottom of the upper cylinder, the bottom and top of the box having a second pair of openings in line with said top and bottom openings respectively, and removable means for closing said second pair of openings, one end of the lower shell being provided with a lateral air inlet into the adjacent air passage, one end of the upper shell being provided with a lateral air inlet into the upper air passage, and the adjacent ends of both shells being provided with openings communicating with the adjacent air passages.

References Cited UNITED STATES PATENTS 2,279,192 4/1942 Brandt 1226 X 2,849,218 8/1958 Cone et al. 263-20 3,189,086 6/1965 Esser et al. 165-155 X 3,238,902 3/1966 Escher 56 FOREIGN PATENTS 243,761 3/ 1963 Australia.

495,359 8/1953 Canada. 1,008,856 5/1957 Germany.

737,297 9/1955 Great Britain.

ROBERT A. OLEARY, Primary Examiner.

A. W, DAVIS, Assistant Examiner, 

1. A RADIATION RECUPERATOR COMPRISING A VERTICAL METAL CYLINDER OPEN AT TOP AND BOTTOM FOR FLOW OF HOT FLUE GASES THERETHROUGH, A METAL SHELL ENCIRCLING THE CYLINDER AND SPACED THEREFROM, MEANS CONNECTING THE UPPER END PORTIONS OF THE CYLINDER AND SHELL TO SUSPEND THE CYLINDER IN THE SHELL, MEANS CLOSING THE SPACE BETWEEN THE LOWER ENDS OF THE CYLINDER AND THE SHELL, AND INSULATING LINING FOR THE SHELL SPACED FROM SAID CYLINDER TO FORM A VERTICAL AIR PASSAGE AROUND THE CYLINDER, THE SHELL BEING PROVIDED AT ITS ONE END WITH A LATERAL AIR INLET INTO SAID PASSAGE AND PROVIDED AT ITS OTHER END WITH A LATERAL AIR OUTLET FROM THE PASSAGE, AND VERTICALLY SPACED METAL RINGS SECURED TO THE INSIDE OF THE SHELL AND EXTENDING RADIALLY INTO SAID LINING FOR SUPPORTING IT AND INTERRUPTING ANY FLOW OF AIR VERTICALLY BETWEEN THE LINING AND SHELL. 